marcin944

my exhaust system on the 944N/A needs to be replaced. one of my friend stold me that i should put in a straight pipe. i know that it definitly is an emission no no, but i would liek to give it a try. however would the oxygen sensor cause any troble with this idea. i would like to take the catalic out, and basically instal a straight pipe welded to a muffler. could anyone help me with this thought?

Adrian

Dear Marcin,
What model 944, what model year. The O2 sensor does not like being left out of the loop. A lot depends upon the type of DME you have installed and this depends on the model year. Get a bypass pipe with the O2 sensor fitting installed. This works. Benefits, well that is another story. I recommend you search the archives of this forum. You will find quite a few posts and threads on this subject.
Ciao,
Adrian
911C4

pete944

I considered replacing the exhaust on my 85.5NA with a Bursh header system and straight pipe, but after reading alot of posts here and on Pelican I changed my mind. The 944 engine needs a certain amount of backpressure and from what I've read removing the cat will cost you in low end torque. A full header exhaust system may only give you 10 or so more horsepower and possibly less torque than the stock system. It's really not worth the expense. It seems that Hans & Franz knew what they were doing when they designed the 944.

Pete

944pilot

My .02 is that I removed the catalytic on my 87NA and repaced it with a piece of 2.5" pipe. I found an imporessive increase in performance. No real numbers, but better throttle response and more power, as far as I could tell, using the seat of the pants method. Granted, my cat may have been pretty clogged up, but I am not sure.
I thought it was a good mod, and my car still passes tailpipe emissions without the cat.

Brian.

community.webshots.com/storage/1/v0/0/2/45/20400245eoEIOLXXyJ_ph.jpg

or

<a href="http://community.webshots.com/storage/1/v3/0/2/20/20400220CEinOZsnPM_ph.jpg" target="_blank">http://community.webshots.com/storage/1/v3/0/2/20/20400220CEinOZsnPM_ph.jpg</a>

944pilot

[img]community.webshots.com/storage/1/v3/0/2/20/20400220CEinOZsnPM_ph.jpg[/img]

JustinL

I had the boys at the local muffler shop pull my cat and put a piece of pipe in as well. The cost was 44 $ canadian. The O2 sensor on my 87 is on the header so this doesn't affect its input. I agree it does feel a little faster, but maybe thats just cause it sounds like a race car now.

If you do pull the cat, don't throw it out incase you ever need to put it back in. But do beware the sound of your car will change dramatically.

Justin

SGOGT4

When you say that the sound will change dramatically is it for the better? I currently have a bursche muffler on my N/A and a set of MSDS headers that I haven't put on yet because there is welding needed. If I am going through the effort, should I also swap out the cat for a test pipe?

Thanks

marcin944

i found a bursch test pipe in pelican for sale and i was thining of putting that on and then welding a straight through muffler on the end. or do you think i should go to a muffler shop and ask them to make me a pipe?

Paladin..

Alright guys...here's my 2 cents from experience. I have an 86 N/A, and when I got it, the exhaust was all still perfectly in tact. On a quest for more power I had a straight pipe installed instead of the catalytic and I retained the o2 sensor (a must). The car felt great...more power, more responsive, but alas...more noise. Not good noise either (personal opinion). Anyway, the MAJOR point here is that within 2 weeks, I blew out a baffle or something in the muffler. So off came the muffler, and on went a straight through Dynomax...What a mistake. The car was so damn loud the tractor-trailer drivers were looking around to see what the hell was coming...and the cops didn't like it either &gt;:-)

What i did to fix this was installed a 6 inch round free flow muffler where tha catalytic was in addition to the dynomax. It had a beautifull sound for about three months. Honestly, it almost sounded like a full blown rally car. Anyway...three months later, I had to take the 6 incher off the car...It was polished stainless, but because it had been so close to the motor, it went gold from the heat of the exhaust, I burnt all of the packing inside, and the perforated tube cracked off at one end. (I'm not hard on my car am I?)

So this summer...I think I'm going to go with a Bursch or MSD header, full 2.5" stainless exhaust with a high flow cat and the muffler from Borla for the Audi TT (1 inlet 2 outs). I thinks the twin outs will look neat against the two corners of the 968 rear.

Anyway...I guess what I'm trying to say is if your gonna mess around with the exhaust, save yourself the headache and agony and do it properly or don't dso it at all.

good luck guys

JustinL

The deep "woof" of the stock exhaust is much louder and that sounds really good. BUT, there's an extra more metallic sound that I don't like so much... This sound only seems to occur at big throttle below 3500. I'd say it sounds halfway between the gurgle of mustangs and the buzzing of civics. Other than that, with the stock muffler it sounds pretty good, especially downshifting.

Justin
red/tan 87

marcin944

my 944 is a 83, so wont i have any problems with the o2 sensor? isnt my sensor located in the pipe. from what i hear, i should just keep the cat with the original pipe, and just change the muffler to a straight trought type.

*Rothmans*

FWIW
From all my experience, this is what I have to offer.
The cat on a 944 is a free flow mesh type that will cause very little restriction - it's huge.
Unless your car has a dirty motor, it should be free flowing. The cat helps muffle the noise substantially.
The muffler is free flowing, but if you want less back pressure, consider using a 951 muffler.
You can also go aftermarket, but why bother?
As well, one of the best exhaust systems I have ever seen out there uses a 2 inch pipe which is smaller than the factory system.
Yes, you need back pressure to assist the motor scavenge the exhaust gases. Unless you are tracking the car leave the cat in.
Consider a free flow muffler.
The smaller diameter pipe will speed up the exhaust gases and will actually produce more torque and horsepower.
Don't waste time and money with headers, there is no power to be found there on a stock motor.
Ultimately you have to live with the noise, so
judge accordingly. Also, bigger is not always better!
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